Add the '-u name' option to the env command, which will completely unset

the given variable name (removing it from the environment, instead of
just setting it to a null value).

PR:		bin/65649
MFC after:	2 weeks

2 files changed, 31 insertions, 8 deletions

diff --git a/usr.bin/env/env.1 b/usr.bin/env/env.1
index a1696d3..cb3980b 100644
--- a/usr.bin/env/env.1
+++ b/usr.bin/env/env.1
@@ -35,7 +35,7 @@
 .\" From FreeBSD: src/usr.bin/printenv/printenv.1,v 1.17 2002/11/26 17:33:35 ru Exp
 .\" $FreeBSD$
 .\"
-.Dd June 20, 2005
+.Dd July 29, 2005
 .Dt ENV 1
 .Os
 .Sh NAME
@@ -46,6 +46,7 @@
 .Op Fl iv
 .Op Fl P Ar altpath
 .Op Fl S Ar string
+.Op Fl u Ar name
 .Op Ar name Ns = Ns Ar value ...
 .Op Ar utility Op Ar argument ...
 .Sh DESCRIPTION
@@ -99,6 +100,21 @@ The
 option recognizes some special character escape sequences and
 also supports environment-variable substitution, as described
 below.
+.\"	-u
+.It Fl u Ar name
+If the environment variable
+.Ar name
+is in the environment, then remove it before processing the
+remaining options.
+This is similar to the
+.Ic unset
+command in
+.Xr sh 1 .
+The value for
+.Ar name
+must not include the
+.Ql =
+character.
 .\"	-v
 .It Fl v
 Print verbose information for each step of processing done by the
@@ -436,12 +452,12 @@ The
 utility conforms to
 .St -p1003.1-2001 .
 The
-.Fl P , S
+.Fl P , S , u
 and
 .Fl v
-options are non-standard
-.Fx
-extensions which may not be available on other operating systems.
+options are non-standard extensions supported by
+.Fx ,
+but which may not be available on other operating systems.
 .Sh HISTORY
 The
 .Nm
diff --git a/usr.bin/env/env.c b/usr.bin/env/env.c
index b11a0b7..34f1e73 100644
--- a/usr.bin/env/env.c
+++ b/usr.bin/env/env.c
@@ -71,7 +71,7 @@ main(int argc, char **argv)
 
 	altpath = NULL;
 	want_clear = 0;
-	while ((ch = getopt(argc, argv, "-iP:S:v")) != -1)
+	while ((ch = getopt(argc, argv, "-iP:S:u:v")) != -1)
 		switch(ch) {
 		case '-':
 		case 'i':
@@ -87,6 +87,13 @@ main(int argc, char **argv)
 			 */
 			split_spaces(optarg, &optind, &argc, &argv);
 			break;
+		case 'u':
+			if (env_verbosity)
+				fprintf(stderr, "#env unset:\t%s\n", optarg);
+			rtrn = unsetenv(optarg);
+			if (rtrn == -1)
+				err(EXIT_FAILURE, "unsetenv %s", optarg);
+			break;
 		case 'v':
 			env_verbosity++;
 			if (env_verbosity > 1)
@@ -135,7 +142,7 @@ static void
 usage(void)
 {
 	(void)fprintf(stderr,
-	    "usage: env [-iv] [-P utilpath] [-S string] [name=value ...]"
-	    " [utility [argument ...]]\n");
+	    "usage: env [-iv] [-P utilpath] [-S string] [-u name]\n"
+	    "           [name=value ...] [utility [argument ...]]\n");
 	exit(1);
 }